Frequency Domain Optical Coherence Tomography Research Articles

Early Vascular Response to Ultrathin Biodegradable Polymer Sirolimus-Eluting Stents for the Treatment of ST-Elevation Myocardial Infarction After Plaque Rupture.

Recent clinical studies suggest that newer-generation drug-eluting stents that combine ultrathin struts and nanocoating (biodegradable polymer sirolimus-eluting stents, BP-SES) could improve long-term clinical outcomes in patients with ST-elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI). However, the early vascular response to BP-SES in these patients has not been investigated so far.We examined this response in 20 patients with STEMI caused by plaque rupture using frequency-domain optical coherence tomography (OCT) to understand the underlying mechanisms. Plaque rupture was diagnosed by OCT before PCI with BP-SES implantation was performed. OCT was again performed before the final angiography (post-PCI) and after 2 weeks (2W-OCT).BP-SES placement caused protrusion of atherothrombotic material into the stent lumen and incomplete stent apposition in all patients. After 2 weeks, incomplete stent apposition was significantly reduced (% malapposed struts: post-PCI 4.7 ± 3.3%; 2W-OCT 0.9 ± 1.2%; P < 0.0001), and the percentage of uncovered struts also significantly decreased (% uncovered struts: post-PCI; 69.8 ± 18.3%: 2W-OCT; 29.6 ± 11.0%, P < 0.0001). The maximum protrusion area of the atherothrombotic burden was significantly reduced (post-PCI 1.36 ± 0.70 mm2; 2W-OCT 0.98 ± 0.55 mm2; P = 0.004).This study on the early vascular responses following BP-SES implantation showed rapid resolution of atherothrombotic material and progression of strut apposition and coverage. (UMIN000041324).

Saline as an Alternative to Radio-Contrast for Optical Coherence Tomography-Guided Percutaneous Coronary Intervention: A Prospective Comparison

ObjectivesTo do a quantitative comparison of saline and contrast Frequency domain optical coherence tomography (FD-OCT) during percutaneous coronary intervention (PCI) optimisation. Methods13 pairs of OCT runs were analysed, wherein each pair consisted of a contrast run and a heparinized saline run taken in the same coronary artery at the same position. Quantitative analysis was done comparing minimal lumen area (MLA), proximal reference diameter (PRD), distal reference diameter (DRD) and percentage area stenosis (AS) at the same anatomical location. Lesion morphologies, rendered stent view and 3D reconstruction were compared for image clarity. ResultThe saline OCT runs resulted in comparable MLA (3.88 ± 2.59 mm2 with saline run vs 3.88 ± 2.71 mm2 with contrast run; p = 0.650), PRD (3.66 ± 0.52 mm with saline vs 3.65 ± 0.52 mm with contrast; p = 0.463), DRD (2.97 ± 0.22 mm with saline vs 2.99 ± 0.88 mm with contrast; p = 0.433), and AS (59.60 ± 18.62% with saline vs 59.18 ± 19.11% with contrast; p = 0.753) with respect to the contrast runs. The Bland Altman plots of the measured parameters indicate good agreement between saline and contrast OCT. Linear regression analysis indicated the absence of proportional bias All lesion morphologies (calcified, fibrotic, thin cap fibroatheroma, macrophages, cholesterol crystals and edge dissection), 3D reconstruction and rendered stent view were clearly demonstrable in the saline OCT runs. ConclusionsUsing heparinized saline as flushing media in coronary FD-OCT may result in vessel dimensions that are comparable with contrast. Heparinized saline may be used as a contrast saving alternative for FD-OCT during PCI optimization.

Optical Coherence Tomography for Ophthalmology Imaging.

Optical coherence tomography (OCT) is a depth-resolved imaging modality, which is able to achieve micrometer-scale resolution within biological tissue noninvasively. In the past 30years, researchers all around the world had made several essential efforts on techniques relevant to OCT. OCT has become a routine process for eye diseases with different types. In this chapter, the three important stages in the development of OCT are briefly illustrated, including the time domain OCT (TD-OCT), the frequency domain OCT (FD-OCT) and the optical coherence tomography angiography (OCTA). Each of the technique has made great progress for use on living human eye imaging in clinical applications. TD-OCT was first proposed and commercialized, which is able to achieve acceptable 2D depth-resolved cross-sectional images of human retina in vivo. FD-OCT was the upgraded OCT technique compared with TD-OCT. By capturing the coherent signal within the Fourier space, the FD-OCT could improve the image sensitivity compared with TD-OCT, and achieve dozens of kilo hertz imaging speed. OCTA is the newest developments of OCT technique, which is able to visualize the micro vasculature networks of human retina in vivo. With OCTA technique, the newest ophthalmologic OCT system is able to achieve detailed diagnosis for both micro-structure and vasculature abnormalities for clinical applications. The further development of OCT technique on imaging speed, contrast, resolution, field of view, and so on will make OCT to be a more powerful tool for clinical usages.

Changes of retinal thickness in macular area of myopia children

Objective: To study the changes of macular retinal thickness in children with moderate and low myopia by frequency domain OCT. Methods: 108 school-age children aged 7-12 years were selected and enrolled into the group. Among them, 58 cases (116 eyes) with simple moderate and low myopia in the myopia group and 50 cases (100 eyes) with straight eyes in the emmetropia group. The retinal thickness in different parts of macular area was compared between the two groups, and the correlation between retinal thickness in different parts of macular area and diopter and axial length was analyzed by Pearson correlation analysis. Results: The length of eye axis in moderate and low myopia group was longer than that in emmetropia group, and the difference was statistically significant (P &lt; 0.05). There was no significant difference in CMT(Central Macular Thickness) and I-AMT(average macular thickness of inner circle) between the two groups (P &gt; 0.05). The AMT(Average Macular Thickness) and O-AMT(average macular thickness of outer circle) in moderate and low myopia group were lower than those in emmetropia group, and the differences were all statistically significant (P &lt; 0.05). The thickness of the retina below the macula and the nasal side was positively correlated with the refractive power in patients with moderate to low-grade myopia (r=0.201, 0.302, P＜0.05), and the thickness of the retina around the macula was negatively correlated with the refractive power (r=-0.326, P＜0.05). Conclusion: There is no significant difference in macular central retinal thickness between children with moderate and low myopia and normal children, and the thickness of paracentral retina tends to become thinner with the deepening of myopia.

Frequency-domain optical coherence tomography with undetected mid-infrared photons

Mid-infrared (mid-IR) light scatters much less than shorter wavelengths, allowing greatly enhanced penetration depths for optical imaging techniques such as optical coherence tomography (OCT). However, both detection and broadband sources in the mid-IR are technologically challenging. Interfering entangled photons in a nonlinear interferometer enables sensing with undetected photons, making mid-IR sources and detectors obsolete. Here we implement mid-IR frequency-domain OCT based on ultra-broadband entangled photon pairs spanning from 3.3 to 4.3 µm. We demonstrate 10 µm axial and 20 µm lateral resolution 2D and 3D imaging of strongly scattering ceramic and paint samples. By intrinsically being limited only by shot noise, we observe times more sensitivity per integration time and power of the probe light. Together with the vastly reduced footprint and technical complexity, our technique can outperform conventional approaches with classical mid-IR light sources.

15685 Predicting onychomycosis clearance at as early as 3 months into the 1-year-long efinaconazole regimen: Role of noninvasive optical coherence tomography imaging

Onychomycosis is the commonest nail disorder, with a prevalence in America of up to 14% (45 million). It can cause local destruction and decreased quality of life. Topical efinaconazole is effective in 54% of cases, but there is no established method for predicting clearance before the 48-week-long regimen ends. FDA-approved noninvasive optical coherence tomography (OCT) imaging has diagnostic capability for onychomycosis. This prospective study evaluated frequency domain (FD) OCT’s prognostic utility for onychomycosis clearance on efinaconazole. 34 subjects were enrolled from 2 sites who had a great toenail with PAS-positive mild to moderate distal lateral subungual onychomycosis as defined by the Onychomycosis Severity Index score. They were treated with efinaconazole topical solution 10% for 48 weeks. OCT was used at weeks 0, 4, 8, 12, and 48. We evaluated onychomycosis findings on 680 OCT scans, including pseudohyphae-like hyperechogenicities in the distal nail plate (thereafter “pseudohyphae”). Our clearance rate matched previous reports (P > .05). We found that pseudohyphae onset between weeks 4 and 12 (P = .018) and pseudohyphae persistence into week 12 (P = .019) predicted PAS-positive nails at week 48, while lack of pseudohyphae up through week 12 predicted PAS-negative clippings (P = .001). Given our results, a FD-OCT scan of the distal nail plate should be obtained at 3 months to evaluate whether to continue efinaconazole daily for 9 additional months. Lack of pseudohyphae at 3 months warrants a re-diagnosis to rule out original false-positive PAS. OCT has the potential to increase both initiation of and compliance with treatment, and decrease the cost and burden of onychomycosis.

Early vascular responses to ultrathin biodegradable polymer sirolimus-eluting stent for the treatment of st-elevation myocardial infarction

Abstract Background Recent clinical study suggests newer-generation drug-eluting stents (DES) that combine ultrathin strut and nano-coating with biodegradable polymers sirolimus-eluting stent (BP-SES) could improve long-term clinical outcomes in patients with ST-elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI) over current generation DES. However, safety profiles in very early phase have not been systematically addressed. Objective and method We exploratory investigate early vascular response following BP-SES implantation in patients with STEMI to reveal mechanism of the favorable clinical outcomes in recent studies using frequency domain-optical coherence tomography (FD-OCT). Consecutive twenty patients with STEMI who underwent FD-OCT immediately after primary PCI and were eligible for follow-up FD-OCT at 2 weeks after implantation were enrolled between June 2018 and November 2019. Results Twenty patients (age 62.7±11.3 years, male 85.0%) were enrolled with frequencies of hypertension (45.0%), diabetes mellitus (35.0%), dyslipidemia (55.0%) and smoking (80.0%). Aspiration catheter were used in all patients, and 1.13±0.34 stents were used. Only one patient (5.0%) received chronic antiplatelet therapy with aspirin prior to the onset of STEMI. All patients started to receive prasugrel as thienopyridine from this event and continued dual antiplatelet therapy for 2 weeks. The percentage of uncovered struts significantly decreased from post-procedure to 2W follow-up (69±18% post-procedure versus 30±11% at 2W follow up, p&amp;lt;0.0001). Malapposed struts also decreased (5.6±5.7% post-procedure versus0.9±1.2% at 2W follow up, p&amp;lt;0.0001).The average protrusion area of athero-thrombotic burden numerically decreased (0.37±0.19 at post-procedure versus 0.34±0.14 mm2 at 2W follow up, p=0.19) and its volume showed similar tendency (10.60±6.40 at post-procedure versus 9.36±5.14 mm3 at 2W follow up, p=0.19). Conclusion(s) This study firstly elucidated very early vascular responses following ultrathin strut BP-SES implantation in STEMI patients, showing early progression of strut coverage and resolution of athero-thrombotic materials. This technology may have a potential to overcome the current generation DESs in this clinical setting. Thrombus, uncovered and malapposed struts Funding Acknowledgement Type of funding source: None

Vascular Response Occurring at 3 Months After Everolimus-Eluting Cobalt-Chromium Stent Implantation in Patients With ST-Segment Elevation Myocardial Infarction vs. Stable Coronary Artery Disease.

Second-generation drug-eluting stents (DES) reduce the incidence of stent thrombosis, even in patients with ST-segment elevated myocardial infarction (STEMI). However, the early local vascular healing after DES implantation in STEMI lesions, which mainly concerns stent thrombosis, is still unclear.Methods and Results:We attempted to determine early local vascular healing 3 months after cobalt-chromium everolimus-eluting stent (CoCr-EES) implantation in STEMI lesions relative to stable coronary artery disease (CAD) lesions. This prospective, multicenter study analyzed 96 total lesions (STEMI=49, stable CAD=51) by frequency domain-optical coherence tomography (FD-OCT) performed post-procedure and at the 3-month follow-up. Although CoCr-EES implanted in STEMI were almost entirely covered at 3 months, they had a relatively high incidence of uncovered struts compared with stable CAD (5.5% vs. 1.6%, P<0.001). Intrastent thrombus in the 2 groups was primarily resolved at the 3-month follow-up (STEMI: 91.7%→26.5%, stable CAD: 74.5%→11.8%). Regarding irregular protrusion, complete resolution was observed in stable CAD (21.6%→0%), while a few stents remained in STEMI (79.2%→8.2%). Although there were almost no changes for the serial change of average lumen area in STEMI, there were slight but significant decreases in stable CAD [STEMI 0.08 (-0.44, 0.55) mm2, stable CAD -0.35 (-0.55, 0.11) mm2; P=0.009]. Although strut coverage after CoCr-EES implantation for STEMI lesions was slightly delayed, the healing process appeared to be acceptable in both STEMI and stable CAD.

Dynamic contrast in scanning microscopic OCT.

While optical coherence tomography (OCT) provides a resolution down to 1 µm, it has difficulties in visualizing cellular structures due to a lack of scattering contrast. By evaluating signal fluctuations, a significant contrast enhancement was demonstrated using time-domain full-field OCT (FF-OCT), which makes cellular and subcellular structures visible. The putative cause of the dynamic OCT signal is the site-dependent active motion of cellular structures in a sub-micrometer range, which provides histology-like contrast. Here we demonstrate dynamic contrast with a scanning frequency-domain OCT (FD-OCT), which we believe has crucial advantages. Given the inherent sectional imaging geometry, scanning FD-OCT provides depth-resolved images across tissue layers, a perspective known from histopathology, much faster and more efficiently than FF-OCT. Both shorter acquisition times and tomographic depth-sectioning reduce the sensitivity of dynamic contrast for bulk tissue motion artifacts and simplify their correction in post-processing. Dynamic contrast makes microscopic FD-OCT a promising tool for the histological analysis of unstained tissues.

Methylene blue-filled biodegradable polymer particles as a contrast agent for optical coherence tomography.

Optical coherence tomography (OCT) images largely lack molecular information or molecular contrast. We address that issue here, reporting on the development of biodegradable micro and nano-spheres loaded with methylene blue (MB) as molecular contrast agents for OCT. MB is a constituent of FDA approved therapies and widely used as a dye in off-label clinical applications. The sequestration of MB within the polymer reduced toxicity and improved signal strength by drastically reducing the production of singlet oxygen and leuco-MB. The former leads to tissue damage and the latter to reduced image contrast. The spheres are also strongly scattering which improves molecular contrast signal localization and enhances signal strength. We demonstrate that these contrast agents may be imaged using both pump-probe OCT and photothermal OCT, using a 830 nm frequency domain OCT system and a 1.3 µm swept source OCT system. We also show that these contrast agents may be functionalized and targeted to specific receptors, e.g. the VCAM receptor known to be overexpressed in inflammation.

Quantization-aware phase retrieval

We address the problem of phase retrieval (PR) from quantized measurements. The goal is to reconstruct a signal from quadratic measurements encoded with a finite precision, which is indeed the case in practical applications. We develop an iterative projected-gradient-type algorithm that recovers the signal subject to ensuring consistency with the measurement, meaning that the recovered signal, when encoded, must yield the same set of measurements that one started with. The algorithm involves rank-1 projection, which stems from the idea of lifting, originally proposed in the context of PhaseLift. The consistency criterion is enforced using a one-sided quadratic cost. We also determine the probability with which different vectors lead to the same set of quantized measurements, which makes it impossible to resolve them. Naturally, this probability depends on how correlated such vectors are, and how coarsely/finely the measurements are quantized. The proposed algorithm is also capable of incorporating a sparsity constraint on the signal. An analysis of the cost function reveals that it is bounded probabilistically, both above and below, by functions that are dependent on how well-correlated the estimate is with the ground-truth. We also derive the Cramér-Rao lower bound (CRB) on the achievable reconstruction accuracy. A comparison with the state-of-the-art algorithms shows that the proposed algorithm has a higher reconstruction accuracy and is about 2 to 3 dB away from the CRB. The edge, in terms of the reconstruction signal-to-noise ratio, over the competing algorithms is higher (about 5 to 6 dB) when the quantization is coarse, thereby making the proposed scheme particularly attractive in such scenarios. We also demonstrate a concrete application of the proposed method to frequency-domain optical-coherence tomography (FDOCT).

Detection and compensation of dispersion mismatch for frequency-domain optical coherence tomography based on A-scan's spectrogram.

Balanced dispersion between reference and sample arms is critical in frequency-domain optical coherence tomography (FD-OCT) to perform imaging with the optimal axial resolution, and the spectroscopic analysis of each voxel in FD-OCT can provide the metric of the spectrogram. Here we revisited dispersion mismatch in the spectrogram view using the spectroscopic analysis of voxels in FD-OCT and uncovered that the dispersion mismatch disturbs the A-scan's spectrogram and reshapes the depth-resolved spectra in the spectrogram. Based on this spectroscopic effect of dispersion mismatch on A-scan's spectrogram, we proposed a numerical method to detect dispersion mismatch and perform dispersion compensation for FD-OCT. The proposed method can visually and quantitatively detect and compensate for dispersion mismatch in FD-OCT, with visualization, high sensitivity, and independence from sample structures. Experimental results of tape and mouse eye suggest that this technique can be an effective method for the detection and compensation of dispersion mismatch in FD-OCT.

Study of saline optical coherence tomography–guided percutaneous coronary intervention (SOCT-PCI Study)

AimThe aim of this study was to evaluate the feasibility of heparinised saline as flushing media for frequency-domain optical coherence tomography (FD-OCT) image acquisition during percutaneous coronary intervention (PCI) optimisation. Methods and resultsTwenty-seven patients undergoing FD-OCT–guided PCI were enrolled. Heparinised saline was injected into the coronary during FD-OCT image acquisition. A total of 118 runs were analysed for image quality and diagnostic value. FD-OCT runs were categorised as follows: good runs (GRs), clinically usable runs (CURs) and clinically not usable runs (NURs); GRs and CURs were combined as clinically effective runs (ERs). Saline FD-OCT enabled visualisation of all possible coronary lesions. Of the 118 runs analysed, 61%, 27.1%, 11.9% and 88.1% were GRs, CURs, NURs and ERs, respectively. Sixty-one percent of total runs were left coronary system (LCS) and 39% were right coronary system (RCS) runs. Among LCS runs, 55.6%, 30.6%, 13.8% and 86.2% were GRs, CURs, NURs and ERs, respectively. Among RCS runs, 69.6%, 21.7%, 8.7% and 91.3% were GRs, CURs, NURs and ERs, respectively. ConclusionThis is the first study to demonstrate the technical feasibility of isolated saline FD-OCT for PCI optimisation.

The image characteristics of optical coherence tomography of the posterior cortical anterior vitreous capsular bag in human eyes

Objective To observe the OCT image characteristics of the posterior cortical anterior vitreous capsular bag (PPVP) in human eyes. Methods A retrospective clinical study. From May 2012 to February 2017, 107 PPVP patients (173 eyes) diagnosed by OCT in Ophthalmology Department of The Third People's Hospital of Chengdu were included in the study. One hundred and three eyes underwent examination of frequency-domain OCT (SD-OCT) and 70 eyes underwent examination of frequency-scanning light source OCT (SS-OCT), respectively. SD-OCT the German Heidelberg Spectralis OCT instrument. SS-OCT was performed by the vitreous enhancement scan mode of Japan's Topcon DRI OCT instrument. The differences of different types of PPVP OCT imaging and image characteristics were observed. Results SD-OCT and SS-OCT showed that the PPVP structure was clear and manifested as macular weakly reflective in the shape of a boat-shaped cavity, the front boundary was vitreous collagen, and the rear boundary was vitreous cortex. There was a weakly reflective Martegiani area on the nasal side of PPVP, and there was a connection channels between them. The two examinations showed a similar pattern, but SS-OCT with the clearer imaging of PPVP. Conclusions The OCT image of PPVP in the human eye is characterized by an anterior weakly reflecting boat-shaped cavity in the macula, with anterior border of vitreous collagen and posterior border of vitreous cortex. Martegiani area is located on the nasal side. Key words: Tomography, optical coherence; Posterior precortical vitreous pockets

The value of color Doppler ultrasound in the detection of macular diseases in age-related cataract patients

Objective To observe the application value with color Doppler flow imaging (CDFI) in the detection of macular diseases in senile cataract. Methods A cross-sectional descriptive study. From December 1 to December 30, 2017, 720 senile cataract patients (1380 eyes) diagnosed in Beijing Tongren Eye Center were included in this study. There were 330 males (629 eyes) and 390 females (751 eyes), with the mean age of 70.35±19.05 years. There were 716 right eyes and 664 left eyes, with the visual acuity 0.05-0.8. The fundus of all the patients can be observed. All patients were examined by OCT using Cirrus HD-Model 5000 produced by German Carl Zeiss company and CDFI using MyLab90 color Doppler ultrasound system produced by ESAOTE S.P.A. Comparing the detection rate of macular lesions between the two methods by using χ2 test. Using statistical methods to evaluate diagnostic tests, a crosstabulation was made to compare the consistency of frequency-domain OCT and CDFI in the diagnosis of macular lesions. Logistic regression analysis of correlation between detection of CDFI macular lesions and central foveal thickness (CFT), average thickness (AT), with or without macular anterior membrane, retinal folds, retinal cystoid edema, hard exudation, macular hole or lamellar macular hole, superficial detachment of neuroepithelium, detachment of pigment epithelium, vitreous macular traction. Results Two hundreds and thirty-nine eyes (17.3%) showed macular disease by OCT, and 161 eyes (11.7%) showed the abnormal echo in the macular region by CDFI. The detection rate of the macular disease between two methods were statistically significant (χ2=851.661, P<0.001), however, the consistency was well (κ=0.766, P=0.000). Logistic analysis showed that the detection rate of macular lesions was related to retinal folds, cysts in retina and CFT (r=1.396, 1.041, 0.12; P<0.01). Conclusion CDFI can effectively detect macular lesions that affect the visual prognosis of senile cataract patients. Key words: Ultrasonography, doppler, color; Macular degeneration; Cataract

Ventricular Fibrillation During Optical Coherence Tomography/Optical Frequency Domain Imaging - A Large Single-Center Experience.

The risks of ventricular fibrillation (Vfib) associated with frequency-domain optical coherence tomography (OCT)/optical frequency domain imaging (OFDI) remain undetermined.Methods and Results:We retrospectively studied the occurrence of Vfib during OCT/OFDI for unselected indications. The frequency of Vfib and patient and procedural characteristics were investigated. A total of 4,467 OCT/OFDI pullback examinations were performed in 1,754 patients (median of 2.0 [2.0-3.0] pullbacks for 1.0 [1.0-1.3] vessels). OCT/OFDI was performed during PCI in 899 patients (51.3%). The contrast injection volume per pullback was 14.4 (11.7-17.2) mL with a flow rate of 3.4 (3.2-3.5) mL/s. Vfib occurred in 31 pullbacks (0.69%) in 30 patients (1.7%). No cases of Vfib occurred when using low-molecular-weight dextran. On multivariate analysis, contrast volume was the only independent factor for predicting Vfib (odds ratio, 1.080; 95% confidence interval, 1.008-1.158, P=0.029). The best cutoff value of contrast volume for predicting Vfib was 19.2 mL (area under the curve, 0.713, P<0.001; diagnostic accuracy, 87.1%). The present large, single-center registry study indicated that Vfib during OCT/OFDI was rare for unselected indications. Contrast injection volume used to displace blood should be limited to avoid Vfib.

Ticagrelor versus clopidogrel in patients undergoing implantation of paclitaxel-eluting stent in the femoropopliteal district: A randomized pilot study using frequency-domain optical coherence tomography

ObjectivesAim of this study was to evaluate different response in platelet reactivity and vessel healing using high-resolution frequency-domain optical coherence tomography (FD-OCT) in patients with femoropopliteal artery disease treated with ZILVER PTX drug eluting stents (DES), and randomly assigned to clopidogrel or ticagrelor for 12 months. BackgroundThe optimal antithrombotic regimen for long-term management of patients with peripheral artery disease (PAD) after revascularization is poorly defined and often extrapolated from trials performed on patients undergoing percutaneous coronary intervention. MethodsIn this single center randomized trial 40 patients with femoropopliteal artery disease treated with ZILVER PTX DES stents, were randomized to Ticagrelor (T) + Aspirin for 3 months, subsequently continuing Ticagrelor alone for another 9 months or Clopidogrel (C) + Aspirin for 3 months, subsequently continuing Clopidogrel alone for 9 months. Platelet reactivity via the P2Y12 pathway was evaluated at baseline and at 3 months follow-up, angiographic and FD-OCT follow-up along the entire stented segment was performed at 12 months. ResultsNo significant difference between T and C group was found concerning net percentage volume obstruction (29.7% ± 17.6% vs. 31.2% ± 10.7%; p = 0.78). FD-OCT at 12 months showed a high percentage of uncovered stent struts in both groups: 24.2% ± 32.8% in the T group vs 15.3% ± 15.8% in the C group (p = 0.4). Mean values of platelet reactivity units (PRU) at 3 month follow-up were 81 ± 72 in the T group and 200 ± 61 in the C group (p < 0.001). ConclusionsSignificantly higher platelet reactivity remains in patients treated with clopidogrel as compared to ticagrelor 3 months after PTA and stent implantation. Ticagrelor does not reduce neointimal proliferation in patients treated with DES in the femoropopliteal district as compared with clopidogrel. A large amount of uncovered stent struts at 12-month follow-up was found in these patients regardless of the antiplatelet treatment assumed.

Optical coherence tomography versus intravascular ultrasound in patients with myocardial infarction: a diagnostic performance study of pre-percutaneous coronary interventions.

Accurate coronary measurements are important in guiding percutaneous coronary intervention. Intravascular ultrasound is a widely accepted diagnostic modality for coronary measurement before percutaneous coronary intervention. The spatial resolution of optical coherence tomography is 10 times larger than that of intravascular ultrasound. The objective of the study was to compare quantitative and qualitative parameters of frequency domain optical coherence tomography (FDOCT) with those of intravascular ultrasound and coronary angiography in patients with acute myocardial infarction. Diagnostic parameters of coronary angiography, intravascular ultrasound, and FDOCT of 250 patients with coronary artery disease who required admission diagnosis were included in the analyses. Minimum lumen diameter detected by FDOCT was larger than that detected by quantitative coronary angiography (2.11±0.1 vs 1.89±0.09 mm, P<0.0001, q=34.67) but smaller than that detected by intravascular ultrasound (2.11±0.1 vs 2.19±0.11 mm, P<0.0001, q=12.61). Minimum lumen area detected by FDOCT was smaller than that detected by intravascular ultrasound (3.41±0.01 vs 3.69±0.01 mm2, P<0.0001). FDOCT detected higher numbers of thrombus, tissue protrusion, dissection, and incomplete stent apposition than those detected by intravascular ultrasound (P<0.0001 for all). More accurate and sensitive results of the coronary lumen can be detected by FDOCT than coronary angiography and intravascular ultrasound (level of evidence: III).

Frequency-domain optical coherence tomography system in the terahertz region

In this study, a frequency-domain optical coherence tomography (FD-OCT) system in the terahertz frequency range was developed. To generate tunable continuous-wave terahertz radiation, the outputs of two near-infrared external cavity diode lasers were mixed in an antenna-coupled photo-mixer. Using the FD-OCT system, tomographic profiling of the front and back surfaces of a high-resistivity silicon plate was realized.

基于压缩感知的频域OCT图像稀疏重构

基于压缩感知的频域OCT图像稀疏重构